Queuing delay based rate control

ABSTRACT

A method and apparatus for rate control adjusts or otherwise requests adjustment of a communication link data rate based on transmit queuing delays. For example, a mobile station may monitor expected transmit queuing delays relative to one or more delay targets or other Quality-of-Service constraints, and request reverse link rate increases or decreases accordingly. Similarly, the mobile station may be configured periodically to request reverse link rate changes based on determining the rate needed to meet targeted queuing delays for one or more service instances being supported by the mobile station in each of a succession of ongoing rate control intervals. Requested rates may be defined data rates or may be virtual rates that can be achieved by using combinations of defined data rates. Queuing-based rate control also can be applied to the base station&#39;s forward link, and, more broadly, to essentially any rate controlled communication link.

BACKGROUND OF THE INVENTION

The present invention generally relates to wireless communicationnetworks, and particularly relates to rate control in such networks.

Rate control is a form of radio link adaptation wherein the transmissionrate from a transmitter to a receiver is adjusted during ongoingcommunications responsive to changing signal quality, network loadingconstraints, etc. As an example, a wireless network base station mayenforce common or per-user reverse link rate control to maintain reverselink loading at or around some targeted level.

Base stations also may enforce or otherwise supervise reverse link ratecontrol of individual mobile stations to meet Quality-of-Service (QoS)requirements that specify maximum delay or jitter limits for reverselink transmissions for particular mobile stations. For example, a givenmobile station may run one or more applications, each having its ownlogical “service instance,” and each potentially having its own QoSrequirements.

Supporting reverse link rate control in this context, the base stationtracks or otherwise monitors indications of reverse link performance foreach mobile station, so that it can determine when rate adjustments arerequired for the individual mobile stations to meet QoS or otherrequirements. Such monitoring requires the mobile stations to provide,i.e., transmit, reverse link information to the base station. Forexample, the mobile stations may provide the base station withinformation regarding their transmit buffer sizes as an indication ofwhether their reverse link rates should be adjusted upward or downward.

With this approach, for example, the base station may grant a higherreverse link rate to a mobile station that has more than a certainamount of pending transmit data buffered. In other words, a large amountof pending transmit data at the mobile station may trigger the basestation to grant a higher rate for one or more subsequent transmitperiods. Obviously, the base station can provide such control only whenit is provided with transmit buffer information from the mobilestations. Thus, the need for additional signaling between the mobilestations and the base station is one drawback of this approach.

Another drawback stems from the approach's failure to directly indicatea pending service problem, i.e., knowledge of a given mobile's transmitbuffer size does not equate to direct knowledge of whether the mobilestation's reverse link performance is at risk of violating QoS or otherservice constraints. For example, the average reverse link throughput ofthe mobile station may be quite high at the current time and, thus, onewould expect even a relatively large transmit buffer to drain quickly.Thus, in addition to receiving transmit buffer size reports from themobile stations, which undesirably adds overhead signaling to thefinite-capacity reverse link, the base station generally has to monitorother conditions, or calculate additional metrics, to determine whetherrate adjustments are needed for particular mobile stations.

SUMMARY OF THE INVENTION

The present invention comprises a method and apparatus wherein transmitrate adjustments are triggered or otherwise initiated based on expectedtransmit queuing delays. For example, if a first transceiver istransmitting data to a second transceiver subject to one or more serviceconstraints, e.g., delay, jitter, etc., it may initiate rate changes forthat radio link responsive to its evaluation of expected transmissionqueuing delays. For example, if the current queue size and currentaverage throughput are such that length of time to empty the queuelikely will violate a delay constraint, then the first transceiver mayrequest or otherwise initiate a rate increase. In general, transceiversevaluate their expected queuing delay(s) in light of known serviceconstraints and determine whether or not to initiate or requestcorrespondingly appropriate rate changes.

In an exemplary embodiment, the present invention is applied to thereverse links between mobile stations and base stations in a wirelesscommunication network, although it should be understood that the presentinvention can be applied to wireless, wired (electrical, optical, etc.)communication links. Thus, an exemplary method of reverse link ratecontrol at a mobile station comprises determining targeted queuingdelays for reverse link transmit data, monitoring transmit data queuesizes and reverse link throughput at the mobile station, and generatingreverse link rate requests based on the transmit data queue sizes, thereverse link throughput, and the targeted queuing delays. The mobilestation may determine targeted delays based on QoS information receivedfrom the network that may be specific to each service instance beingsupported by the mobile station. Thus, the mobile station may receivetargeted queuing delay information for one or more service instancesbeing supported by the mobile station, periodically calculate anexpected queuing delay for each service instance, and request a reverselink rate increase if any expected queuing delay exceeds a first delayvalue based on a targeted delay for the corresponding service instance,or request a reverse link rate decrease if the expected queuing delayfor each service instance falls below a second delay value based on thetargeted delay for the service instance.

Another exemplary embodiment comprises receiving targeted queuing delayinformation for one or more service instances being supported by themobile station, and periodically calculating an overall data raterequired to achieve targeted queuing delays for the service instancesand requesting a rate change based on the overall data rate. The mobilestation may periodically calculate an overall data rate required toachieve targeted queuing delays for the service instances by calculatinga required data rate for each service instance needed to achieve thetargeted queuing delay for that service instance in a next rate controlperiod, and calculating the overall data rate based on the required datarates of the service instances. With the overall data rate thuscalculated, the mobile station may request the nearest appropriatedefined data rate, assuming that the mobile station is constrained tooperate at one in a set of defined data rates.

Alternatively, the mobile station may use a rate dithering approach,wherein it maps the desired overall rate into an “effective” or“virtual” data rate that can be achieved using one or more combinationsof defined data rates. The mobile station would thus request theappropriate virtual rate. In turn, an exemplary base station comprisestransmitter circuits to transmit signals to a plurality of mobilestations, receiver circuits to receive signals from a plurality ofmobile stations, and processing circuits, including a rate controlprocessor, to determine whether to deny or grant rate adjustmentrequests received from one or more mobile stations and to grantnon-standard rate requests by mapping each non-standard rate requestinto a standard set of rates based on selecting one or more combinationsof the standard rates.

Of course, the present invention is not limited by these exemplarydetails. Moreover, those skilled in the art will recognize additionalfeatures and advantages provided by the present invention upon readingthe following discussion, and upon viewing the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an exemplary wireless communication networkaccording to an exemplary embodiment of the present invention.

FIG. 2 is a diagram of exemplary queuing delay based rate controlprocessing.

FIG. 3 is a diagram of exemplary event-triggered rate controlprocessing.

FIG. 4 is a diagram of exemplary base and mobile stations.

FIG. 5 is a diagram of exemplary periodic averaging/dithering ratecontrol processing.

FIG. 6 is a diagram of exemplary virtual rate mapping.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an exemplary wireless communication network 10 thatcommunicatively couples a plurality of mobile stations 12 to one or morePublic Data Networks (PDNs) 14, such as the Internet. As illustrated,network 10 comprises a Radio Access Network (RAN) 16 that is coupled tothe PDNs 14 a Packet Switched Core Network (PSCN) 18, which may comprisevarious Internet Protocol (IP) packet routers, gateways, and one or moreauthentication/authorization entities. Those skilled in the art shouldthus appreciate that network 10 as depicted is simplified for clarityand in actuality may include additional elements, such as CircuitSwitched Core Network (CSCN) coupling RAN 16 to the Public SwitchedTelephone Network (PSTN). Further, it should be noted that network 10may be configured according to various network standards, such as, amongothers, IS-2000 or Wideband CDMA (WCDMA) standards.

Regardless, RAN 16 provides the wireless interface to the mobilestations 12 via forward and reverse radio links that may supportper-mobile forward and reverse link traffic and control channels, one ormore “broadcast” channels used for paging and common control, and one ormore shared channels subject to scheduled use. In any case, an exemplaryRAN 16 comprises one or more base stations, each comprising a BaseStation Controller (BSC) 20 and one or more associated Radio BaseStations (RBSs) 22. BSC 20 may include packet data processingfunctionality for direct connection to PSCN 18, or may be coupled toPSCN 18 through a Packet Control Function (PCF) 24 or like entity.

In an exemplary embodiment as applied to reverse link rate control ofthe mobile stations 12, each mobile station 12 has a rate-controlledreverse link channel, e.g., a Reverse Link Packet Data Channel (R-PDCH)assigned to it, and the data rate of that channel can be adjusted upwardor downward by the RBS 22 responsive to rate control request messagessent from the mobile station 12. Thus, according to FIG. 2, network 10may send QoS information, e.g., targeted queuing delay information orother service constraint information, to the mobile station 12 fromwhich it determines targeted reverse link transmit queuing delays (Step100). That is, if a given service instance being supported by the mobilestation has specific delay or jitter constraints associated with it,then there are limits on how long data to be transmitted from the mobilestation 12 for that service instance can “wait” in the mobile station'stransmit queue.

In operation, then, mobile station 12 monitors its transmit buffer size,i.e., its transmit data queue(s), and keeps track of its average reverselink throughput (Step 102). By maintaining a running average or otherperiodically updated estimate of its reverse link throughput, the mobilestation 12 can estimate how long given data will remain in its transmitqueue, or how long it will take to drain data that already is queued.Thus, mobile station 12 can generate link rate change requests based onthe average throughput, the queue size(s), and the targeted queuingdelays (Step 104). In other words, the mobile station 12 generates ratechange requests based on determining expected reverse link queuingdelays and evaluating those expected delays relative to one or moreservice constraints. Those skilled in the art will appreciate that thesame or similar logic could be applied by the RBS 22 or BSC 20 to theforward link, wherein expected queuing delays could be used to triggerforward link transmit rate adjustments, changes in forward linkscheduling priorities, or both.

FIG. 3 illustrates an exemplary event-triggered embodiment wherein themobile station 12 determines targeted queuing delays for each serviceinstance being supported by it (Step 110). In operation, then, mobilestation 12 monitors the transmit queue size and throughput for eachservice instance (Step 112), and periodically evaluates the expectedqueuing delay for each service instance (Step 114). If the expectedqueuing delay of any service instance exceeds the targeted delay forthat service instance (Step 116), mobile station 12 may initiate a rateincrease by sending a rate change request message to RBS 22. If none ofthe expected queuing delays exceed their corresponding target delays,mobile station 12 may check whether all of the expected delays fallbelow corresponding targeted delays (Step 122). If so, mobile station 12may initiate a rate decrease by sending a rate change request message toRBS 22. Note that the comparison of expected-to-targeted queuing delaysfor rate increases may be different than for rate decreases. That is,the mobile station 12 may implement hysteresis or other rate changesmoothing control by calculating different target delays for use inSteps 116 and 120.

In looking at target delay calculations in more detail, one may assumethat each mobile station 12 is provided with either a maximum Radio LinkProtocol (RLP) buffer delay requirement or a target delay value thatshould be maintained in order to reduce jitter at the initiation of eachservice instance. One also may assume that the user class, if any, ofthe mobile station 12 is known. Such information, if desired, may beused to determine the settings for certain rate control parameters. Forexample, if a maximum delay threshold of τ_(max) is required then onemay define an associated target delay value as τ=θ·τ_(max), wherein thevalue of θ depends on, for example, the outage probability of theapplication, i.e., the probability that the delay exceeds the specifiedthreshold τ_(max), and the user class of the mobile station 12. Anexemplary method attempts to maintain the average queuing delay at τ. Ifa target delay is specified for jitter guarantees, then mobile station12 may be configured to set the target delay to that value.

Thus, let τ_(i) denote the target delay for service instance i. On aperiodic basis, such as every T seconds, mobile station 12 computes afiltered estimate u_(i) in bits-per-second (bps) of the throughput sofar achieved for service instance i. It also monitors the present sizeb_(i) in bits of the transmit queue for the service instance andestimates the expected queuing delay of a pending RLP frame to betransmitted as by d_(i)=b_(i)/u_(i). If d_(i)>ατ_(i) for any serviceinstance i, then mobile station 12 transmits a rate increase request toRBS 22. Conversely, if d_(i)<βτ_(i) for all service instances, themobile station 12 sends a rate decrease request to RBS 22. Otherwise,mobile station 12 may choose to maintain its present reverse link rate.The parameters 0≦α≦1 and 0≦β≦1 may be determined by the user class ofmobile station 12. For example, both parameters can be set closer to oneas the user class preference increases. In the case of a jitterconstrained application these parameters also may depend on thetightness of the jitter constraints. Naturally this approach can begeneralized to multiple thresholds.

In any case, the rate request transmitted from the mobile station 12will depend on the threshold region within which the present delayestimate lies. Before sending a rate increase request, the mobilestation 12 first checks to see if its power headroom is large enough tosupport the higher rate. If not, the request is not sent. Additionally,one can enhance the above operations by taking into account the effectof a rate request command. For example, if a rate increase request isgranted then in the next rate control period the mobile station's queuewill drain twice as fast, assuming that a grant results in a doubling ofdata rate. Conversely, if a rate decrease is granted then the queue willdrain half as fast, again assuming that a rate decrease halves the datarate. Such information can be used in making better decisions for α, β,T, and the buffer size(s). For example, the values of α and β can be setbased on the granularity of the defined rate change steps. Here, onenotes that the mobile station's buffer capacities implicitly are assumedto be sufficient to support a queue equal to the product of the maximumrate and the maximum target delay. If not, then Adaptive QueueManagement (AQM) techniques may be used.

Mobile stations 12 may be configured to support the above and otherexemplary embodiments of the present invention. By way of non-limitingexample, FIG. 4 illustrates exemplary mobile station and RBSconfigurations that may be used to support the present invention asapplied to either or both forward and reverse link rate control. Mobilestation 12 comprises an antenna assembly 30, a receiver circuit 32, atransmitter circuit 34, a baseband processor circuit 36, includingtransmit buffer memory 38 and a rate control circuit 40, and furthercomprises a system controller 42 and an associated user interface 44.RBS 22 comprises receive/transmit antenna elements 50, pooled receivercircuits 52 and associated reverse link processing circuits 54, pooledtransmitter circuits 56 and associated forward link processing circuits58, and interface and control circuits 60, including a rate/schedulingcontrol circuit 62. Those skilled in the art should appreciate thatthese mobile station and RBS depictions represent exemplary functionalarrangements and, because these entities typically comprise one or moremicroprocessor/digital signal processors, or collections of suchprocessing resources, other functional arrangements may be used asneeded or desired.

Regarding mobile station 12, rate control circuit 40, which may beimplemented in hardware, software, or some combination thereof,functions as a rate controller that perform exemplary rate controlprocessing in accordance with the present invention. Thus, it may trackor otherwise have access to average throughput information for allservice instances being supported by mobile station 12, and may monitortransmit buffer queue sizes as part of its rate control operations.Thus, it may monitor queue size and throughput information for eachservice instance being supported by the mobile station 12, and generaterate control requests for transmission to RBS 22. In turn, RBS 22, e.g.,via rate/scheduling control circuit 62, may respond to those requestsaccordingly. For example, if mobile station 12 transmits a rate increaserequest, RBS 22 and/or BSC 20 may grant or deny the request according toongoing loading conditions or other criteria.

In another exemplary embodiment, mobile station 12 may be configured toembody the processing logic of FIG. 4, wherein queuing delay-based ratecontrol is performed on a periodic basis. Such an approach may be usedto maintain the average queuing delay at or near some specified value.With this approach, the mobile station may, for each service rate,compute the reverse link data rate that, if used in the next controlinterval, results in an expected delay of τ_(i) at the end of thecontrol interval. In other words, mobile station 12 consistentlyattempts to change the rate so that the targeted queuing delay isachieved at the end of the control interval. Thus, the rate, λ_(i), thatshould be requested for the next rate control interval is given by,

${\lambda_{i} = {\frac{{u_{i}\tau_{i}} - b_{i}}{T} + u_{i}}},$which gives the desired rate for service instance i. Thus, the overalldata rate required for the next rate control service interval isdetermined based on the desired rates of all service instances includedin the evaluation, which typically comprises all service instances beingsupported by the mobile station 12. Thus, the overall rate, λ, thatshould be requested for the next rate control interval that will allowthe mobile station 12 to achieve the targeted queuing delays for allservice instances of concern is given as

$\lambda = {\sum\limits_{i = 1}^{i = N}\;{\lambda_{i}.}}$

Commonly, however, only defined data rates may be requested by mobilestation 12. That is, the network standards on which network 10 isconfigured, e.g., IS-2000, WCDMA, etc., may provide for a set of definedreverse link data rates. Thus, mobile station 12 may be configured tomap the overall desired data rate into the set of defined data ratesbased on selecting the closest defined rate that will allow it to atleast meet the targeted queuing delays over the next control interval.The selected rate, {tilde over (λ)}, is thus requested by the mobilestation 12.

As an alternative to choosing a defined rate, the mobile station 12 andnetwork 10 may be configured to adopt a “rate dithering” approach,wherein the mobile station 12 and RBS 22 or BSC 20 are configured with“virtual rate” tables that represent effective data rates that can beachieved by assigning one or more combinations of defined data rates.For example, suppose that the mobile station 12 determines an overalldesired rate, λ, as the summation of the targeted rates, λ_(i), for allservice instances i. Rather than mapping the overall rate into thedefined rate set, mobile station 12 computes or otherwise selects avirtual data rate, e.g., from configured data in its memory, andtransmits a request to the RBS 22 that identifies that virtual rate. Inturn, RBS 22 or BSC 20 processes that virtual rate by determining theappropriate combination of defined rates that will effect that virtualrate over some defined number of transmit intervals. Such mapping may bebased on configured virtual rate tables held in memory at the RBS 22that maps virtual rates to corresponding combinations of defined ratesand transmit intervals.

Thus, in one embodiment, both mobile station 12 and RBS 22 (or BSC 20)contain tables that map combinations of N (non-unique) rates to thecorresponding average rate. Assuming K supportable rates, then suchmapping results in K^(N) virtual” rates. Note that the method may takeinto account re-transmissions, etc., in such computations. Mobilestation 12 thus can map the desired overall rate to the nearest virtualrate and send the request to the RBS 22, which in turn looks up thesequence of defined rates that should be granted to the mobile station12 for the next N frames that achieves this virtual rate. Use of virtualrates in this manner reduces rate fluctuations associated with servicingthe transmit queues, while still meeting the desired QoS guarantees. Byway of non-limiting example, assume that N=2, and that defined rates 2,3, and 4 are supported and an average of two transmissions is needed perframe. The possible virtual rates (after H-ARQ) are 1, 1.25, 1.5, 1.75,and 2. If, for example, the mobile station 12 requires a rate of 1.23 itcan request a rate of 2×1:25=2:5 from the RBS 22. In turn, the RBS 22can allow the mobile station 12 to achieve this rate by granting it arate of 3 for a first transmit frame and a rate of 2 for the secondtransmit frame.

FIG. 5 illustrates exemplary processing logic to implement the aboverate average and rate dithering methods. Processing begins with theassumption that mobile station 12 receives targeted queuing delay orother QoS information as needed for each service instance, and that itmaintains ongoing throughput and queue size information values as neededfor each service instance (Step 130). For periodic rate controladjustment, mobile station 12 may be configured to implement a ratecontrol timer in hardware or software that sets the control interval forrate adjustments (Step 132). If it is time for a rate control adjustment(Step 134), mobile station 12 computes a target data rate needed toachieve the targeted queuing delay for each service instance i asexplained above.

Mobile station 12 initializes i to 1 and sets its overall desired rateto “x,” which may be zero or some other value (Step 136). For the ithservice instance, mobile station 12 calculates the target rate requiredto achieve the targeted delay in the next control interval (Step 138),and adds that rate to the overall desired rate (Step 140). If there aremore service instances (Step 142), mobile station 12 increments i andrepeats the target rate and overall desired rate calculations for thenext service instance.

Upon finishing such calculations for the last service instance, themobile station 12 may perform either the defined rate or virtual ratemapping as described above (Step 146-1 or 146-2). That is, mobilestation 12 may directly map the overall desired rate into the set ofdefined rates, or it may map that value into a set of virtual rates. Ineither case, mobile station 12 sends a rate request message for the nextrate control interval (Step 148).

Assuming that mobile station 12 requested a virtual rate, FIG. 6illustrates exemplary processing at RBS 22, wherein the RBS 22 receivesthe rate control request identifying the requested virtual rate (Step160). RBS 22 accesses its stored virtual rate table(s) to look up thecombination of defined rates and corresponding transmit intervals thatshould be used to achieve the virtual rate (Step 162). In this respect,rate/scheduling control circuit 62, or some other digital processinglogic circuit in RBS 22, can be configured to access a memory-basedlookup table that is configured with the virtual-to-defined ratemappings. Regardless, RBS 22 determines the corresponding standard ratesand grants them to mobile station 12 for the required number of frames(Step 164).

Of course, those skilled in the art will recognize that rate ditheringusing such virtual rates, or rate average as described above, are notessential to the present invention. Indeed, whether event-triggered, ordriven by periodic rate averaging/dithering, the present inventionprovides a method whereby radio link rate adjustments are made based onthe evaluation of expected/targeted queuing delays relative to QoSrequirements or other performance constraints.

Such radio link adjustments, as noted earlier herein, are not limited tothe reverse link and, indeed, the present invention provides exemplaryqueuing-based forward link control in one or more base stationembodiments. For example, various third generation (3G) networkstandards, such as 1XEV-DV, 1XEV-DO, and WCDMA, use a shared high-speedchannel in the forward link to transmit data for a plurality of dataconnections corresponding to a group of users, i.e., a given group ofmobile stations 12. At any given instant, the shared channel typicallycarries traffic for only one data connection, but over time all usersreceive data via the shared channel based on “scheduling” operationscarried out at RBS 22, wherein the RBS 22 transmits traffic for selecteddata connection(s) in each of an ongoing sequence of schedulingintervals.

Thus, in such embodiments, RBS 22 allows users to time-share one or moreforward link communication channels, and assigns a scheduling utilityfunction to each data connection of a user sharing the channel. In anexemplary embodiment, rate/scheduling control circuit 62 is configuredto implement a scheduler that tries to maximize the total utilityfunction, which may be based on joint evaluation of the individualutility functions. In any case, if a particular data connection has adelay constraint (e.g, a limit on the maximum delay or a jitterconstraint) then this constraint can be included in the correspondingutility function. Thus, the scheduling priority of a given dataconnection may be made dependent on the expected queuing delays for thatconnection and, in particular, may be made to depend on the expectedqueuing delays relative to that connection's targeted queuing delays.

For example, rate/scheduling control circuit 62 may receive or haveaccess to QoS constraints associated with one or more of the dataconnections. Thus, a given data connection may have a jitter-imposedtargeted queuing delay of qt, and the rate/scheduling control circuit 62may be configured to maintain the queuing delay as close as possible toqt. As such, the utility function for that data connection can beconfigured as U(q)=−(q−qt)², where the expected queuing delay, q, isestimated as described above for the reverse link. RBS 22 maintains anestimate of the forward link throughput for the data connection and,whenever a scheduling decision is to be made, it estimates the delay asthe ratio of the queue length and the throughput. Thus, RBS 22 candetect when the expected queuing delays of any data connection exceedthat connection's targeted delays and adjust the scheduling prioritiesaccordingly. Therefore, RBS 22 applies essentially the same logic as themobile station does in making rate control requests based on queuingdelays but instead of making rate requests, RBS 22 changes userscheduling priorities based on queuing delays.

Of course, it should be understood that rate/scheduling control circuit62 can be configured to make scheduling adjustments and/or make forwardlink rate adjustments based on expected queuing delays. For example, ifRBS 22 serves a plurality of mobile stations 12 using dedicated,rate-adjustable forward link communication channels, rate/schedulingcontrol circuit 62 can be configured to initiate rate adjustments onthose channels as a function of expected versus targeted queuing delaysfor outgoing traffic.

Therefore, the present invention may be applied to forward and reverselink rate control, forward link scheduling control, or to combinationsthereof in a variety of wireless communication network types. Indeed,the present invention is not limited to wireless applications and may beapplied to both wireless and wired communication links. As such, thepresent invention is not limited by the foregoing discussion and,indeed, is limited only by the following claims and their reasonableequivalents.

1. A method of reverse link rate control at a mobile station comprising:determining targeted queuing delays at the mobile station for reverselink transmit data; monitoring transmit data queue sizes and ongoingreverse link throughput at the mobile station expressed as currentaverage throughput for data transmissions by the mobile terminal on thereverse link; and generating reverse link rate requests at the mobilestation based on determining whether targeted queuing delay violationsare expected given the transmit data queue sizes and the ongoing reverselink throughput, the reverse link rate requests being further based on,in each rate control period, determining a data rate neededsubstantially to meet targeted queuing delays in the next rate controlperiod for each service instance being supported by the mobile station.2. The method of claim 1, wherein determining targeted queuing delaysfor reverse link transmit data comprises determining a targeted queuingdelay for each service instance being supported by the mobile station.3. The method of claim 2, wherein monitoring transmit data queue sizesand ongoing reverse link throughput comprises monitoring a transmit dataqueue size and an ongoing reverse link throughput for each serviceinstance.
 4. The method of claim 3, wherein generating reverse link raterequests based on the transmit data queue sizes, the ongoing reverselink throughput, and the targeted queuing delays comprises determiningwhether an expected queuing delay of any service instance exceeds atarget queuing delay for that service instance and, if so, requesting areverse link rate increase.
 5. The method of claim 3, wherein generatingreverse link rate requests based on the transmit data queue sizes, theongoing reverse link throughput, and the targeted queuing delayscomprises determining whether expected queuing delays for all serviceinstances are below target queuing delays defined for the serviceinstances and, if so, requesting a reverse link rate decrease.
 6. Themethod of claim 2, wherein determining a targeted queuing delay for eachservice instance being supported by the mobile station comprisesreceiving service instance delay requirements from a wirelesscommunication network supporting the mobile station.
 7. The method ofclaim 1, wherein generating reverse link rate requests based on thetransmit data queue sizes, the ongoing reverse link throughput, and thetargeted queuing delays comprises generating reverse link rate requestson an event-triggered basis by comparing expected queuing delays foreach of one or more service instances to targeted queuing delaysassociated with those service instances.
 8. The method of claim 1,wherein generating reverse link rate requests based on the transmit dataqueue sizes, the ongoing reverse link throughput, and the targetedqueuing delays comprises generating reverse link rate requests on aperiodic basis to control an average queuing delay of the mobile stationrelative to a targeted queuing delay.
 9. The method of claim 1, whereindetermining a data rate needed substantially to meet targeted queuingdelays in the next rate control period for each service instance beingsupported by the mobile station comprises: for each service instance,computing a data rate required to meet the targeted queuing delay forthat service instance in the next rate control period; and calculatingan aggregate data rate based on the data rates computed for the serviceinstances being supported by the mobile station.
 10. The method of claim9, further comprising selecting one among a set of defined data ratesbased on the calculated aggregate data rate, and requesting the selectedone of the defined data rates for the next rate control period.
 11. Themethod of claim 1, wherein generating reverse link rate requests basedon the transmit data queue sizes, the ongoing reverse link throughput,and the targeted queuing delays comprises determining a required datarate that satisfies a targeted queuing delay for reverse link datatransmissions over a given interval, calculating an effective data ratefrom the required data rate that can be achieved using one or morecombinations of defined data rates, and requesting the effective datarate.
 12. A method of reverse link rate control at a mobile stationcomprising: receiving targeted queuing delay information for one or moreservice instances being supported by the mobile station; periodicallycalculating an expected queuing delay at the mobile station for eachservice instance; requesting a reverse link rate increase by the mobilestation if any expected queuing delay exceeds a first delay value basedon a targeted delay for the corresponding service instance; andrequesting a reverse link rate decrease by the mobile station if theexpected queuing delay for each service instance falls below a seconddelay value based on the targeted delay for the service instance,wherein requesting a reverse link rate increase or decrease is based on,in each rate control period, determining a data rate neededsubstantially to meet targeted queuing delays in the next rate controlperiod for each service instance being supported by the mobile station.13. The method of claim 12, further comprising computing the first delayvalue for each service instance by scaling the targeted delay for thatservice instance by a first factor and computing the second delay valuefor each service instance by scaling the targeted delay for that serviceinstance by a second factor.
 14. The method of claim 13, furthercomprising setting at least one of the first and second factors based ona granularity of defined rate change steps.
 15. The method of claim 13,further comprising setting at least one of the first and second factorsbased on a subscriber class association of the mobile station.
 16. Themethod of claim 13, further comprising adjusting a rate control intervalfor periodically calculating the expected queuing delay for each serviceinstance based on whether a requested reverse link rate increase ordecrease was granted.
 17. The method of claim 12, wherein periodicallycalculating an expected queuing delay for each service instancecomprises, for each service instance, calculating an expected queuingdelay for one or more Radio Link Protocol (RLP) frames to be transmittedbased on an average transmit data throughput for that service instance,and a current queue size for that service instance.
 18. The method ofclaim 17, further comprising tracking an average transmit datathroughput for each service instance.
 19. A method of reverse link ratecontrol at a mobile station comprising: receiving targeted queuing delayinformation for one or more service instances being supported by themobile station; and periodically calculating an overall data raterequired to achieve targeted queuing delays for the service instancesand requesting a rate change by the mobile station based on the overalldata rate, wherein requesting a rate change is based on, in each ratecontrol period, determining a data rate needed substantially to meettargeted queuing delays in the next rate control period for each serviceinstance being supported by the mobile station.
 20. The method of claim19, wherein periodically calculating an overall data rate required toachieve targeted queuing delays for the service instances comprises:calculating a required data rate for each service instance needed toachieve the targeted queuing delay for that service instance in a nextrate control period; and calculating the overall data rate based on therequired data rates of the service instances.
 21. The method of claim19, wherein requesting a rate change based on the overall data ratecomprises requesting one in a set of defined data rates that will allowthe mobile station to achieve the targeted queuing delays for theservice instances.
 22. The method of claim 19, wherein requesting a ratechange based on the overall data rate comprises selecting an effectivedata rate based on the overall data rate, wherein the effective datarate represents one or more combinations of defined data rates andcorresponding transmit intervals.
 23. A mobile station for use in awireless communication network comprising: a receiver circuit to receivesignals transmitted by the network; a transmitter circuit to transmitsignals, including rate requests, to the network; and a rate controllercircuit configured to: determine targeted queuing delays for reverselink transmit data; monitor transmit data queue sizes and ongoingreverse link throughput at the mobile station, the ongoing reverse linkthroughput being expressed as current average throughput for datatransmissions by the mobile station on a reverse link; and generatereverse link rate requests based on determining whether targeted queuingdelay violations are expected given the transmit data queue sizes andthe ongoing reverse link throughput, the reverse link rate requestsbeing further based on, in each rate control period, determining a datarate needed substantially to meet targeted queuing delays in the nextrate control period for each service instance being supported by themobile station.
 24. The mobile station of claim 23, wherein the ratecontroller circuit is configured to determine targeted queuing delaysfor reverse link transmit data by determining a targeted queuing delayfor each service instance being supported by the mobile station.
 25. Themobile station of claim 24, wherein the rate controller circuit isconfigured to monitor transmit data queue sizes and ongoing reverse linkthroughput at the mobile station by monitoring a transmit data queuesize and an ongoing reverse link throughput for each service instance.26. The mobile station of claim 25, wherein the rate controller circuitis configured to generate reverse link rate requests based on thetransmit data queue sizes, the ongoing reverse link throughput, and thetargeted queuing delays by determining whether an expected queuing delayof any service instance exceeds a target queuing delay for that serviceinstance and, if so, requesting a reverse link rate increase.
 27. Themobile station of claim 25, wherein the rate controller circuit isconfigured to generate reverse link rate requests based on the transmitdata queue sizes, the ongoing reverse link throughput, and the targetedqueuing delays by determining whether expected queuing delays for allservice instances are below target queuing delays defined for theservice instances and, if so, requesting a reverse link rate decrease.28. The mobile station of claim 24, wherein the rate controller circuitis configured to determine a targeted queuing delay for each serviceinstance being supported by the mobile station by receiving serviceinstance delay requirements from a wireless communication networksupporting the mobile station.
 29. The mobile station of claim 23,wherein the rate controller circuit is configured to generate reverselink rate requests based on the transmit data queue sizes, the ongoingreverse link throughput, and the targeted queuing delays by generatingreverse link rate requests on an event-triggered basis by comparingexpected queuing delays for each of one or more service instances totargeted queuing delays associated with those service instances.
 30. Themobile station of claim 23, wherein the rate controller circuit isconfigured to generate reverse link rate requests based on the transmitdata queue sizes, the ongoing reverse link throughput, and the targetedqueuing delays by generating reverse link rate requests on a periodicbasis to control an average queuing delay of the mobile station relativeto a targeted queuing delay.
 31. The mobile station of claim 23, whereinthe rate controller circuit is configured to determine a data rateneeded substantially to meet targeted queuing delays in the next ratecontrol period for each service instance being supported by the mobilestation by: for each service instance, computing a data rate required tomeet the targeted queuing delay for that service instance in the nextrate control period; and calculating an aggregate data rate based on thedata rates computed for the service instances being supported by themobile station.
 32. The mobile station of claim 31, wherein the ratecontroller circuit is configured to select one among a set of defineddata rates based on the calculated aggregate data rate, and request theselected one of the defined data rates for the next rate control period.33. The mobile station of claim 23, wherein the rate controller circuitis configured to generate reverse link rate requests based on thetransmit data queue sizes, the ongoing reverse link throughput, and thetargeted queuing delays by determining a required data rate thatsatisfies a targeted queuing delay for reverse link data transmissionsover a given interval, calculating an effective data rate from therequired data rate that can be achieved using one or more combinationsof defined data rates, and requesting the effective data rate.
 34. Amethod of forward link control at a radio base station comprising:determining targeted queuing delays at the radio base station for one ormore data connections being used to serve a plurality of mobile stationson one or more forward link communication channels; determining expectedqueuing delays at the radio base station for the data connections bymonitoring transmit data queue sizes and forward link throughput for thedata connections; adjusting at least one of a scheduling priority and aforward link data rate at the radio base station for a given dataconnection based on the expected and targeted queuing delays; andconfiguring scheduling utility functions used to determine thescheduling priorities of the data connections to be dependent on theexpected queuing delays so that the priority for each data connectionincreases if the expected queuing delay exceeds the targeted queuingdelay of the data connection.
 35. The method of claim 34, wherein theone or more data connections are supported on a shared forward linkcommunication channel that serves the plurality of mobile stations, andwherein adjusting at least one of a scheduling priority and a forwardlink data rate for a given data connection based on the expected andtargeted queuing delays comprises adjusting the scheduling priority ofone or more data connections over one or more scheduling intervalsresponsive to determining that the expected queuing delays exceed thetargeted queuing delays.
 36. The method of claim 34, wherein adjustingat least one of a scheduling priority and a forward link data rate for agiven data connection based on the expected and targeted queuing delayscomprises in a given forward link service interval, adjusting theforward link data rate for the given connection responsive todetermining that the expected queuing delay exceeds the targeted queuingdelay.
 37. The method of claim 34, wherein determining targeted queuingdelays for one or more data connections being used to serve a pluralityof mobile stations on one or more forward link communication channelscomprises determining Quality-of-Service requirements associated witheach data connection.
 38. A base station for use in a wirelesscommunication network comprising: transmitter circuits to transmitsignals to a plurality of mobile stations receiver circuits to receivesignals from a plurality of mobile stations; and processing circuits,including a rate control processor, to determine whether to deny orgrant rate adjustment requests received from one or more mobile stationsand to grant non-standard rate requests by mapping each non-standardrate request into a standard set of rates based on selecting one or morecombinations of the standard rates.
 39. The base station of claim 38,wherein mapping each non-standard rate request into a standard set ofrates based on selecting one or more combinations of the standard ratescomprises selecting at least a first standard rate to be used by arequesting mobile station for a first number of transmit intervals and asecond standard rate to be used by the requesting mobile station for asecond number of transmit intervals.
 40. The base station of claim 38,wherein mapping each non-standard rate request into a standard set ofrates based on selecting one or more combinations of the standard ratescomprises selecting two or more standard rates to be used by arequesting mobile station over one or more defined transmit intervalssuch that an effective rate achieved by the requesting mobile stationover the one or more defined transmit intervals substantially equals thenon-standard rate requested by the requesting mobile station.